Imaging faint sources within a speckle halo with synchronous interferometric speckle subtraction

The performance of high-contrast imaging systems is very often limited by the presence of speckles in the point-spread function (PSF) of the central source. Since this unwanted light is coherent with the central source, it is possible to make it interfere with light extracted from the center of the PSF. The light of a faint companion, however, will not interfere with the central source. By taking advantage of this fundamental difference, it is possible to detect faint companions superposed on speckles more than 100 times brighter, even if the speckles are rapidly "boiling." Possible optical designs to use this technique on interferometers or imaging telescopes are shown, and a data analysis algorithm is proposed. Synchronous interferometric speckle suppression greatly improves the performance of ground-based telescopes with adaptive optics systems for direct imaging of faint companions. On a space telescope, where the speckle lifetime is expected to be longer, companions 10⁴ times fainter than the speckle halo can be detected in a few minutes.